Perry Smith wrote:
What I want to do is create a table that has a unique id and a string which will be the type. The other tables that type will point to will have the same id and the attributes for that type. So, the first table may be items and items could reference people, companies, etc. The key to people, companies, etc is the same id as for item -- i.e. if you union all of the sub tables, you will have each id at most one time.
Your description above contains much that we allow Rails and AR to manage for us. One of the key things with Rails is that primary keys are meaningless to us. Only AR cares about them, and we let it take control of them to make it easier for us to focus on the application itself rather than the management of the data the app uses. You'll find it a lot easier to work with Rails, and to get help here too IME, if you can start by answering: "From a user perspective, what problem are you solving? What is it you're trying to allow the user to do with your application?"
I believe, using PostgreSQL's features, this will be easier to keep consistent. Of course, I may find out that I'm full of BS.
I haven't used PostgreSQL with Rails, but don't have the impression from seeing OP's posts that it's any easier or harder than any other supported DB with Rails.
But, part of the knowledge I need to gain is how ActiveRecord goes from the blob of mess that the database returns to an instance of a particular class.
Depending on exactly what your objective is, you may or may not need to know the above in order to achieve your objective. Probably not. In general, our apps deal in objects, we tell AR how the objects are related, it handles the ORM mapping, and we're happy for it.
If anyone can help me out and tell me where to look, etc, that would be much appreciated.
I'd start out by trying to regain my "beginner eyes." Will Rogers said "It's not what we don't know that hurts. It's what we know that ain't true." To be successful with Rails, you're probably going to do quite a bit of 'unlearning.' That's just speculation on my part, based on a year and a half of observation / participation here on the list.
There are a number of beginner tutorials out there. With all things Rails, Google is your friend. You may find it too elementary for you, but you might want to start with: